Female relative not initially let loose? (5)
I believe the answer is:
untie
'let loose?' is the definition.
(I've seen this in another clue)
'female relative not initially' is the wordplay.
'female relative' becomes 'auntie' (I've seen this before).
'not initially' means to remove the first letter.
'auntie' with its first letter taken off is 'UNTIE'.
(Other definitions for untie that I've seen before include "Release from bonds or open shoelace" , "Free from restraining bonds or ropes" , "Release, loosen" , "Free from binds" , "Undo a knot" .)